In a thin film transistor liquid crystal display (TFT-LCD), by means of utilizing the intensity variation of an electric field across a liquid crystal layer, the orientation of liquid crystal molecules is changed, and thus the strength of transmitted light is controlled to display an image. Generally speaking, a complete liquid crystal display panel must have a backlight module, a polarizer, an upper substrate and a lower substrate, and a layer of liquid crystal molecules filled in a cell composed of the two substrates.
An electric field generated in a liquid crystal display is substantially perpendicular to a substrate plane, and is used to control the state of liquid crystal molecules. This liquid crystal display is generally referred to as a vertical electric field type liquid crystal display. In the vertical electric field type liquid crystal display, a first electrode is formed on a lower substrate sandwiching a liquid crystal layer, a second electrode is formed on an upper substrate, and after a voltage is applied to them, an electric field substantially perpendicular to the substrate plane that begins from the first electrode and guides to the second electrode will be formed.
An electric field generated in a liquid crystal display is substantially parallel to a substrate plane, and is used to control the state of liquid crystal molecules. This liquid crystal display is generally referred to as a transverse electric field type liquid crystal display. In the transverse electric field type liquid crystal display, a first electrode and a second electrode are usually formed on a lower substrate sandwiching a liquid crystal layer, and after a voltage is applied to them, an electric field substantially parallel to the substrate plane that begins from the first electrode and guides to the second electrode will be formed.
In prior art, there is also a case that a liquid crystal display with a vertical electric field and a transverse electric field is manufactured by combining advantages of the vertical electric field and the transverse electric field. As shown in FIG. 1, the liquid crystal display includes an upper substrate 5 and a lower substrate 6, and a liquid crystal layer 30 filled between the upper substrate 5 and the lower substrate 6. Herein, the upper substrate 5 includes a first electrode (common electrode) 1 on a side close to the liquid crystal layer 30, and the lower substrate 6 includes a second electrode (common electrode) 2 and a third electrode (pixel electrode) 3 that are located on a side close to the liquid crystal layer 30. After a voltage is applied, the first electrode 1 and the second electrode 2 are equal in electric potential, and no electric field is generated between them. The first electrode 1 and the third electrode 3 are unequal in electric potential, and a vertical electric field perpendicular to the substrate plane is generated. The second electrode 2 and the third electrode 3 are unequal in electric potential, and a transverse electric field parallel to the substrate plane is generated.
Compared with the transverse electric field type liquid crystal display, the number of bright and dark stripes in the liquid crystal display with the vertical electric field and the transverse electric field can be reduced. However, in a space region between the second electrode 2 and the third electrode 3 in this substrate, the deflection degree of liquid crystal molecules is still inadequate, thereby resulting in a fact that a corresponding zone is not bright enough. Namely, the display quality of the liquid crystal display may be affected. In this case, if an adequate brightness needs to be ensured, then it is necessary for a driving voltage of the second electrode 2 and the third electrode 3 to be increased.